Full marks to director Neil Marshall, who gave us Dog Soldiers and The Descent, for putting the corpulent Roman epic on a crash diet; it's just a shame his rationing extended to the plot and characters too. Centurion is basically a succession of chase sequences, lean and sinewy, as Michael Fassbender's resolute commander leads a dirty half-dozen of survivors on a fraught dash through northern Britain, with the Picts in close pursuit. Along the way, Marshall pauses briefly to take in the sights. There are eye-gougings and amputations and a skimpy romantic sub-plot, all but concealed behind the desaturated geysers of blood. In its hell-for-leather fashion this works just fine, though there is something dogged – even joyless – about the way it sets about its task. This is exercise-bike cinema: energetic, relentless and tipping towards monotony.